Alkyl phosphinates can be prepared by the reaction of an olefin with an alkali metal salt of hypophosphorous acid. For example, the reaction of alpha-olefins with sodium hypophosphite yields sodium alkyl phosphinates when initiated photochemically or by an introduced chemical source of free radicals such as a peroxide. The reaction may be summarized as follows: ##STR1##
The alkyl phosphinate can be converted into the corresponding phosphonate (RCH.sub.2 CH.sub.2 P(O)(ONa).sub.2) by exposure to an oxidizing agent. Both the alkyl phosphonates and alkyl phosphinates can function as anionic surfactants, and can act to enhance the wetting power of aqueous media.
Commonly-assigned U.S. Pat. No. 4,590,014, discloses that high-yield reactions of an olefinic material with a hypophosphite salt to yield a phosphinate salt can be accomplished by a process comprising simultaneously adding the olefinic material and essentially all of the free radical source used to initiate the reaction to a hot solution of the hypophosphite salt. In preferred embodiments of the invention, an alcohol solution of the olefinic compound and the free radical source are added to the hypo-phosphite in an aqueous alcoholic reaction medium. During the addition, the hypophosphite solution is maintained at a temperature at or slightly above the decomposition temperature of the free radical source. After the addition is completed, the reaction mixture can be heated for a period of time sufficient to complete the reaction.
Commonly-assigned U.S. patent application Ser. No. 838,097, discloses that the photo-initiated reaction of an olefinic material with a hypophosphite salt to afford a phosphinate salt can be accomplished in high yields by a process comprising simultaneously adding the olefinic material and essentially all of the photo-initiator to a solution of the hypophosphite salt in an aqueous alcoholic reaction medium. During the addition, the hypophosphite solution is irradiated with a source of ultraviolet light. After the addition is completed, the reaction mixture is irradiated and heated for a period of time sufficient to complete the reaction.
Wolf (U.S. Pat. No. 4,590,014) and Ser. No. 838,097 also disclose that alkyl phosphinates prepared according to these processes strongly complex alkaline earth metal ions, i.e., calcium ion, and are more effective sequestering agents than the corresponding alkyl phosphonates. This result indicates that water-soluble alkyl phosphinates will be effective as builders and conditioners in detergent formulations, where they will function as substitutes or replacements for commonly-used sequestering agents such as citrates, hydroxy malonates, nitrilotriacetates and the like. These sequestering agents act to prevent or inhibit metal cations responsible for water hardness such as Ca.sup.++ or Mg.sup.++ from precipitating commonly-used alkali metal builder salts and anionic surfactants.
Therefore, a need exists for new phosphinated and phosphonated compounds which are effective to sequester water hardness factors.